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Thread: IBR Ratings

  1. #1
    Join Date
    Aug 2003
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    IBR Ratings

    After a heat loss is done, which BTU output rating is used? I have seen conflicting info on different websites, even from Weil-Mcclain themselves. Various people claim to use the I=B=R Rating others claim to use the DOE Rating, including Weil themselves.

    CGI - 6 Weil Boiler Specs Input - 167 MBH DOE Heating Capacity - 140 MBH Net I=B=R Water rating - 122 MBH If you us the IBR its an almost 20,000 btu difference, so which is correct???

  2. #2
    Join Date
    Mar 2007
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    Myrtle Beach, SC
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    IBR rating allows for piping losses. On AC that is the same as duct gain and loss.

    When I was up north, we used IBR ratings.
    Remember, Air Conditioning begins with AIR.

  3. #3
    Join Date
    Jun 2007
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    Minneapolis, MN
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    IBR is not as valid today as in the past as we now use smaller pipes, reset, lower water temperatures, etc. Still a good idea for cast iron boilers on old big pipe, high mass radiator systems.

    MA

  4. #4
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    Boiler location, and how and where the pipes are run determine if you need to use IBR, or DOE ratings.

    DOE rating calculates that all heat lost by the boiler through its insulation and jacket, plus any heat lost by the pipes heat the house.(like duct work in the conditioned space)

    IBR rating calculates all heat lost by both boiler and pipes is lost to the house(ducts in an unconditioned space)
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  5. #5
    Join Date
    Jun 2007
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    Minneapolis, MN
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    I believe an unhealthy majority still us net IBR rating as THE sizing factor. This assumes that 15% of the net output of the boiler is lost before it gets to the conditioned space.

    If the pipes are in the conditioned space -still in the conditioned envelope- this heat is not lost. We could debate system efficiency - how fast the heat lost is replaced by the boiler - but the net heat output DOE is not lost.

    When you use IBR output - 15% too big by definition - then add the typical 10 to 20% "fudge" factor your customer gets over 25% more boiler than he needs. He will never know the difference but we should.

    MA

  6. #6
    Join Date
    Jul 2004
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    Much of the IBR factor is for a cold start application. It's call "Pick-up" and can account for up to 15% of the boiler capacity. It's really not accurate to say one method is better than the other because in some instances, IBR is a minimum need while in other instances even the DOE has a healthy margin. This is where it takes a true professional to determine which rating to use, IMO.
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  7. #7
    Join Date
    Jun 2007
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    A subtle observation. Were it that all our fellows were so astute.

    MA
    Last edited by BadgerBoiler MN; 11-23-2007 at 11:19 PM. Reason: grammar

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